Mobile telecommunication system base station, mobile terminal

ABSTRACT

If, in a mobile telecommunication system comprising at least one mobile terminal, at least one base station and at least one processor device for processing signalling messages, such as an exchange, the signalling messages to be transmitted from the mobile terminal are provided with a first destination code if they are destined for the exchange and with a second destination code if they are destined for the base station, the signalling messages provided with the first destination code are able to pass through the base station transparently without extensive analyses being necessary in the base station. Preferably, signalling messages to be transmitted from the exchange are provided with a terminal destination code if they are destined for the mobile terminal and with a base station destination code if they are destined for the base station, signalling messages provided with a terminal destination code being returned to the exchange by the base station if the link with the mobile terminal is not functioning well.

BACKGROUND OF THE INVENTION

The invention relates to a mobile telecommunication system comprising

at least one processor device for processing signalling messages,

at least one base station coupled to the processor device, and

at least one mobile terminal which can be coupled to the base station.

Such a mobile telecommunication system is disclosed in the paperentitled "Application of Signalling System No. 7 to Public Land MobileNetworks: Status and Evolution" by Jan A. Audestad in Telektronikk No.1, 1990, 621.391.037.37:621.396.931. The mobile telecommunication systemdescribed therein comprises a processor device for processing signallingmessages (in FIG. 1 of the said paper, this relates to an MSC or mobileswitching center, and in another case, it relates, for example, to an LEor local exchange), a base station (in FIG. 1 of the said paper, thisrelates to a BSS or base station system) and a mobile terminal (in FIG.1 of the said paper, this relates to an MS or mobile station).Signalling messages which have to be processed in the processor deviceare, for example, a call set-up message and a location update message,in contrast to signalling messages which are processed in the basestation, such as, for example, a resource management message. In thisconnection, a base station is defined as the whole of an intelligent BSCor base station controller and one or more aerials which are eachcoupled to a BST or base station transceiver and which are controlled bythe BSC. The base station and the processor device are mutually coupled,for example via a physical connection, and the mobile terminal and thebase station can be mutually coupled, for example via a radio link. Inthis known mobile telecommunication system, the mobile terminal (alowest-ranked ranked entity) transmits signalling messages to the basestation (an entity with lowest-but-one ranking) which analyzes saidsignalling messages by investigating which mobile terminal thesignalling messages originate from (on the basis of a frequency and/ortime-slot analysis or on the basis of an analysis of a link identifier)and by analyzing the content of the signalling messages, and thendetermining, on the basis of the preceding analyses, which entity theyare destined for. Depending on the analysis result, some signallingmessages are passed to the processor device (a higher-ranked entity) andother signalling messages are retained for a further processing.

Provided the mobile terminal is located in the base area of the basestation, certain analytical processes proceed in the base station whichhave to be terminated in the base station as soon as the mobile terminalmoves to an adjacent base area of an adjacent base station (a so-calledhandover procedure) and which have to be started up in the adjacent basestation. The known mobile telecommunication system has, inter alia, thedisadvantage that, for example, in the case of a handover procedure in abase station, analytical processes have to be terminated and preciselythe same analytical processes have to be started up in an adjacent basestation.

SUMMARY OF THE INVENTION

The object of the invention is, inter alia, to provide a mobiletelecommunication system of the type mentioned in the preamble in whichthe starting-up and termination of analytical processes are handled moreefficiently.

For this purpose, the mobile telecommunication system according to theinvention has the characteristic that signalling messages to betransmitted from the mobile terminal to the processor device via thebase station are provided with a first destination code, signallingmessages to be transmitted from the mobile terminal to the base stationbeing provided with a second destination code.

By providing signalling messages to be transmitted from the mobileterminal with a first destination code if they are destined for theprocessor device and providing them with a second destination code ifthey are destined for the base station, signalling messages providedwith a first destination code are able to pass through the base stationtransparently. As a result, it is no longer necessary to arrange for abase station to analyse all signalling messages originating from themobile terminal and certain analytical processes can therefore beavoided in the base station.

The invention is based, inter alia, on the insight that, for example, inthe case of a handover procedure, the analytical processes to beterminated in a base station and precisely the same analytical processesto be set up in an adjacent base station can be replaced bycorresponding analytical processes which proceed in a higher-rankingentity and which, in the case of a handover procedure, no longer have tobe terminated and set up elsewhere if the higher entity is incommunication with both the base station and the adjacent base station.Said higher entity is reached most efficiently if intervening entitiesare able to be passed through in a transparent manner, which becomespossible by adding the destination codes to the signalling messages.

The addition of destination codes to signalling messages does notexclude the possibility that two signalling messages are togetherprovided with one destination code and does not even exclude thepossibility of splitting three signalling messages into two parts, thefirst signalling message and the first half of the second signallingmessage being provided with a destination code and the second half ofthe second signalling message and the third signalling message beingprovided with a destination code.

A first embodiment of the mobile telecommunication system according tothe invention has the characteristic that the base station is providedwith comparison means for comparing first and second destination codesof signalling messages with at least one predetermined value and fortransmitting, in response to a comparison result in one sense, asignalling message in the direction of the processor device and, inresponse to a comparison result in another sense for retaining asignalling message.

By using said comparison means, whether, a signalling message should betransmitted in the direction of the processor device or should beretained is determined in a simple manner in the base station on thebasis of a destination code.

A second embodiment of the mobile telecommunication system according tothe invention has the characteristic that signalling messages to betransmitted from the base station to the processor device are providedwith a third destination code, the processor device being provided withcomparison means for comparing first and third destination codes ofsignalling messages with at least one predetermined value and fortransmitting, in response to a comparison result in one sense, asignalling message and, in response to a comparison result in anothersense, for retaining a signalling message.

By providing signalling messages to be transmitted from the base stationwith a third destination code if they are destined for the processordevice and, for example, providing them with a fourth destination codeif they are destined for a higher-ranking processor device (a stillhigher-ranking entity), signalling messages not destined for theprocessor device are able to pass through the processor devicetransparently. By using the comparison means, whether a signallingmessage should be transmitted in the direction of a higher-rankingprocessor device or should be retained is determined in a simple mannerin the processor device on the basis of a destination code.

The first and third destination code may either correspond to oneanother in their entirety or differ to a greater or lesser extent. Onlythe fact that the processor device is able to recognize both destinationcodes as being destined for it is of importance. The first, second,third and fourth destination code may furthermore be of the explicittype or of the implicit type. In the case of destination codes of theexplicit type, one particular base station or one particular processordevice is indicated, the possibility even arising of a mobile terminaltransmitting a signalling message provided with a second destinationcode to a base station A, said second destination code relating to abase station B, after which the base station A transmits said signallingmessage to a processor device which then transmits the signallingmessage to the base station B. In the case of destination codes of theimplicit type, for example, a type of entity (base station, processordevice) or a type of functionality (for example, call handling) isindicated, the base station and the processor device having to bepreprogrammed with data relating to which type of entity they are orwith data relating to the functionalities which it is possible to carryout on the spot.

A third embodiment of the mobile telecommunication system according tothe invention has the characteristic that signalling messages to betransmitted from the processor device to the mobile terminal via thebase station are provided with a terminal destination code, signallingmessages to be transmitted from the processor device to the base stationbeing provided with a base-station destination code, and the basestation being provided with detection means for detecting base-stationdestination codes and, in response thereto, retaining a signallingmessage and for detecting terminal destination codes and, in responsethereto, transmitting a signalling message in the direction of themobile terminal.

By providing signalling messages to be transmitted from the processordevice to the mobile terminal via the base station with a terminaldestination code and providing signalling messages to be transmittedfrom the processor device to the base station with a base-stationdestination code, whether a signalling message should be transmitted inthe direction of the mobile terminal or should be retained is determinedin a simple manner in the base station on the basis of a destinationcode by using the detection means. The base station destination code mayindicate a certain base station directly, but it may also indicate aconnection indirectly, via which connection the base station can bereached. In this case, the base-station destination code comprises oneor more connection codes.

It should be pointed out that it is known from the said paper to dividesignalling messages to be exchanged between the base station and theprocessor device into two types, signalling messages of one type beingtransmitted via a DTAP protocol and signalling messages of the othertype being transmitted via a BSSMAP protocol. However, it is true ofboth types of signalling messages that whether a signalling messagebelongs to one type or to the other type is clear only after anextensive analysis of the content of the signalling message. In the caseof the mobile telecommunication system according to the invention, suchanalytical processes are avoided.

It should furthermore be pointed out that it is generally known toinsert a link identifier in a signalling message. However, it is againtrue of such a link identifier (for example, call id) that which linkidentifier is contained in a signalling message is clear only after anextensive analytical process. In the mobile telecommunication systemaccording to the invention, such an analytical process is avoided.

A fourth embodiment of the mobile telecommunication system according tothe invention has the characteristic that the processor device isprovided with

memory means for storing at least one coupling between a terminaldestination code and a base-station destination code for each mobileterminal, and

adjustment means coupled to the memory means for adjusting, in responseto an adjustment message, at least one coupling stored in the memorymeans, the base station being provided with

link detection means for detecting whether or not a link between thebase station and the mobile terminal is functioning well, and

return means coupled to the link detection means for returning asignalling message provided with a terminal destination code to theprocessor device in response to it having been detected that the link isnot functioning well.

On the basis of couplings stored in the memory means, via which basestation each mobile terminal receives the signalling messages isdetermined in the processor device. This stored information may beadjusted by the adjustment means in response to an adjustment messageoriginating, for example, from a higher-ranking processor device. Suchan adjustment message then comprises at least one indication of whichcoupling it relates to or which terminal destination code (and possiblywhich old base-station destination code) and an indication of which newbase-station destination code it relates to. As soon as the linkdetection means in the base station have detected that a link betweenthe base station and the mobile terminal is not functioning well, thereturn means return the signalling message provided with a terminaldestination code to the processor device. Because the processor devicereceives a signalling message provided with a terminal destination code,it is known, in the case of the processor device, that said signallingmessage has not been able to reach the terminal and the processor devicemay, for example, retransmit the signalling message on the basis of theinformation stored in the memory means or wait until said informationhas been adjusted in response to an adjustment message. The linkdetection means present in the base station may be designed in variousways, for example as a transmitter/receiver which transmits a code wordto the mobile terminal during each time interval and, in responsethereto, should receive a (further) code word, or as atransmitter/receiver which adds a code word to each signalling messageto be transmitted and should receive a (further) code word for eachsignalling message to be received, or as a receiver which detects thereceived power of the radio signal.

A fifth embodiment of the mobile telecommunication system according tothe invention has the characteristic that the base station is providedwith adjustment-message generating means coupled to the link detectionmeans for generating an adjustment message.

In this case, the base station generates the adjustment message. In thecase of a forward handover procedure, said adjustment message willoriginate from the next base station (which base station shouldtherefore be adequately informed by the mobile terminal), the adjustmentmessage having transmitted from the adjacent base station to theprocessor device, preferably before the signalling message provided withthe terminal destination code is returned to the processor device fromthe (old) base station. In the case of a backward handover procedure,said adjustment message will originate from the (old) base station, theadjustment message having to be transmitted from the (old) base stationto the processor device, preferably before the signalling messageprovided with the terminal destination code is returned to the processordevice from the (old) base station. In both cases, this can be achievedin a simple manner by retaining the signalling message to be returnedand provided with a terminal destination code in the (old) base stationfor some time (for example, 100 msec) before it is actually returned. Inthe case of a backward handover procedure, instead of introducing thedisadvantageous delay time (of, for example, 100 msec), use may also bemade of a certain sequence relationship, signalling messages only beingreturned after the adjustment message has been transmitted.

A sixth embodiment of the mobile telecommunication system according tothe invention has the characteristic that the mobile terminal isprovided with

link detection means for detecting whether or not a link between thebase station and the mobile terminal is functioning well, and

adjustment-message generating means coupled to the link detection meansfor generating an adjustment message.

In this case, the mobile terminal generates the adjustment message. Asregards the link detection means present in the mobile terminal, thesame is true as for the link detection means present in the basestation, and both the forward handover procedure and the backwardhandover procedure can be used. Furthermore, it is conceivable that themobile terminal dispatches two adjustment messages, one for the basestation and one for the processor device, or that the mobile terminaldispatches adjustment messages via both base stations.

The invention furthermore relates to a base station for use in a mobiletelecommunication system.

The base station according to the invention has the characteristic thatthe base station is provided with comparison means for comparing firstand second destination codes of signalling messages originating from amobile terminal with at least one predetermined value and fortransmitting, in response to a comparison result in one sense, asignalling message in the direction of a processor device and, inresponse to a comparison result in another sense, for retaining asignalling message.

A first embodiment of the base station according to the invention hasthe characteristic that the base station is provided with generatingmeans for generating a signalling message having a third destinationcode and being destined for the processor device.

A second embodiment of the base station according to the invention hasthe characteristic that the base station is provided with detectionmeans for detecting base-station destination codes and, in responsethereto, retaining a signalling message, and for detecting terminaldestination codes and, in response thereto, transmitting a signallingmessage in the direction of a mobile terminal.

A third embodiment of the base station according to the invention hasthe characteristic that the base station is provided with

link detection means for detecting whether or not a link between thebase station and the mobile terminal is functioning well, and

return means coupled to the link detection means for returning asignalling message provided with a terminal destination code to theprocessor device in response to it having been detected that the link isnot functioning well.

A fourth embodiment of the base station according to the invention hasthe characteristic that the base station is provided withadjustment-message generating means coupled to the link detection meansfor generating an adjustment message.

The invention also relates furthermore to a mobile terminal for use in amobile telecommunication system.

The mobile terminal according to the invention has the characteristicthat the mobile terminal is provided with generating means forgenerating a signalling message having a first destination code andbeing destined for a processor device and for generating a signallingmessage having a second destination code and being destined for a basestation.

A first embodiment of the mobile terminal according to the invention hasthe characteristic that the mobile terminal is provided with

link detection means for detecting whether or not a link between thebase station and the mobile terminal is functioning well, and

adjustment-message generating means coupled to the link detection meansfor generating an adjustment message.

From EP 0 558 041, it is known to transmit so-called "broadcast data"from a processor device to a mobile terminal via one or more basestations. It is not known therefrom to transmit signalling messages froma mobile terminal to a base station, on the one hand, and to a processordevice via a base station, on the other hand, said signalling messagesbeing provided with destination codes.

"Application of Signalling System No. 7 to Public Land Mobile Networks:Status and Evolution", by Jan A. Audestad, in Telektronikk No. 1, 1990,621.391.037.37:621.396.931.

EP 0 558 041

All references are deemed to be incorporated in this application.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail with reference to anexemplary embodiment shown in the figures. In the figures:

FIG. 1 shows an overview of a telecommunication system according to theinvention,

FIG. 2 shows a base station according to the invention for use in thetelecommunication system according to the invention,

FIG. 3 shows a mobile terminal according to the invention for use in thetelecommunication system according to the invention,

FIG. 4 shows a signalling message for use in the telecommunicationsystem according to the invention, and

FIG. 5 shows an adjustment message for use in the telecommunicationsystem according to the invention.

DETAILED DESCRIPTION

The telecommunication system according to the invention shown in FIG. 1comprises a base station 1 which is coupled via a radio link 5 to amobile terminal 2 which can be coupled via a radio link 6 to a basestation 3 (after a handover procedure). Base station 1 is coupled via aconnection 7 to a processor device 4 for processing signalling messages,such as, for example, a local exchange (LE) or a mobile switching center(MSC) which is coupled via a connection 8 to base station 3 and which iscoupled via a connection 9 to a higher entity (such as an IN servicecontrol point).

The base station 1 shown in FIG. 2 comprises a transceiver 10 which iscoupled to radio link 5, a transceiver 11 which is coupled to a furtherradio link and a transceiver 12 which is coupled to yet a further radiolink. Outputs of transceivers 10, 11 and 12 are each coupled to a firstinput, a second input and a third input, respectively, of comparisonmeans 13, a first output of which is coupled to network termination (NT)14, which is connected to connection 7. A second output of comparisonmeans 13 is coupled to a first input of processor 16, an output of whichis coupled to an input of generating means 17. An output thereof iscoupled to a second input of NT 14. A second input of processor 16 iscoupled to a first output of detection means 15, an input of which iscoupled to an output of NT 14. A second output of detection means 15 iscoupled to a first input of return means 18, of which a first output, asecond output and a third output are coupled to an input of transceiver10, transceiver 11 and transceiver 12, respectively. A fourth output ofreturn means 18 is coupled to a third input of NT 14, and a second inputof return means 18 is coupled to a first output of adjustment-messagegenerating means 19, a second output of which is coupled to a fourthinput of NT 14. A first input, a second input and a third input ofadjustment-message generating means 19 are coupled to a control outputof transceiver 10, transceiver 11 and transceiver 12, respectively. Eachtransceiver comprises link detection means coupled to the controloutput, transmitting means coupled to the input for transmitting via theradio link signalling messages received via the input, and receivingmeans coupled to the output for receiving, via the radio link, asignalling message transmitted by a mobile terminal and for generatingsaid received signalling message at the output. NT 14 has a transmitterfor transmitting, via connection 7, signalling messages which have beenreceived via the first, second, third and/or fourth input, and it has areceiver for receiving signalling messages transmitted via connection 7by a processor device and for generating received signalling messages atthe output.

As regards signalling messages originating from higher entities, thebase station 1 shown in FIG. 2 functions as follows. A signallingmessage which arrives via connection 7 and is provided with either abase-station destination code or a terminal destination code is receivedby NT 14, which dispatches said signalling message to detection means15. In the case of a base-station destination code, this is detected bydetection means 15, for example by comparing the base-stationdestination code with a predetermined value. If equality is found, thena base-station destination code is involved and the signalling messageis fed to processor 16 which processes it further. In the case of aterminal destination code, this is detected by detection means 15, forexample by comparing the terminal destination code with thepredetermined value. If inequality is found, then a terminal destinationcode is involved and the signalling message is fed via return means 18,which store the signalling message, to a transceiver 10, 11 or 12. Thechoice of the transceiver is made on the basis of the terminaldestination code, for example by detection means 15 and/or return means18 by consulting a table or by involving processor 16 in the procedure.The signalling message is optionally extended temporarily with a certaintransceiver code. The chosen transceiver then transmits the signallingmessage via the associated radio link to the mobile terminal associatedwith the terminal destination code. The signalling message istransmitted by the transceiver only if the associated radio link isfunctioning correctly. If this is not the case, it is detected by thelink detection means contained in each transceiver, and in response tothis, a signal is transmitted from the transceiver concerned toadjustment-message generating means 19. The latter generate anadjustment message and send it to NT 14 for transmission via connection7 and convey the signal, provided with the particular transceiver code,to return means 18 which also transmit the signalling message, which isstill stored, to NT14 for transmission via connection 7.

As regards signalling messages originating from a mobile terminal, thebase station 1 shown in FIG. 2 functions as follows. A signallingmessage which arrives via radio link 5 and is provided with either afirst or a second destination code is received by transceiver 10, whichtransmits it to comparison means 13. The latter compare the destinationcode with a predetermined value, for example a value which correspondsto the second destination code, and in the event of equality, thesignalling message is obviously destined for the base station and is fedto processor 16 for further processing. In the event of inequality, thesignalling message is destined for a higher entity, for example an LE,and it is fed to NT 14 for further transmission via connection 7.

As regards signalling messages to be transmitted to processor device 4or to a still higher-ranked entity, the base station 1 shown in FIG. 2functions as follows. If processor 16 wishes to dispatch a signallingmessage to a higher-ranked entity, it transmits said signalling messageto generating means 17 which add, for example, under the control ofprocessor 16 a third (that is to say destined for processor device 4) ora fourth (that is to say destined for a still higher-ranked entity)destination code to the signalling message and then feed the entiresignalling message to NT 14 for transmission via connection 7.

If transceivers 10, 11 and 12 receive signalling messages from mobileterminals on the basis of different time slots, two different signallingmessages will never arrive at the same time, so that no problems willarise in comparison means 13 either. If, on the other hand, saidtransceivers receive signalling messages on the basis of differentfrequencies, there is the possibility that two different signallingmessages arrive precisely at the same time. In this last case, therewill have to be buffers either in transceivers 10, 11 and 12 or incomparison means 13. As a consequence of the complexity of base station1, most of the units 10 to 19 inclusive shown in FIG. 2 will be providedwith buffers in order to prevent undesirable interactions betweendifferent signals unless use is made of a further processor, not shownin FIG. 2, for controlling, in particular, comparison means 13,detection means 15, return means 18 and adjustment-message generatingmeans 19. However, it is also possible for processor 16 to beresponsible for these tasks.

The mobile terminal 2 shown in FIG. 3 comprises a transceiver 20, afirst output of which is coupled to an input of a processor 21. Anoutput of processor 21 is coupled to an input of generating means 22, anoutput of which is coupled to a first input of transceiver 20. A secondoutput thereof is coupled to an input of adjustment-message generatingmeans 23, an output of which is coupled to a second input of transceiver20.

The operation of mobile terminal 2 is as follows. A signalling messagearriving via radio link 5 is received by transceiver 20 which transmitsit to processor 21 for further processing. If processor 21 wishes todispatch a signalling message to base station 1 or a higher-rankedentity, it transmits said signalling message to generating means 22which add, for example, under the control of processor 21 a first (thatis to say destined for processor device 4) or second (that is to saydestined for base station 1) destination code to the signalling messageand then feed the entire signalling message to transceiver 20 fortransmission via radio link 5. The signalling message is transmitted bytransceiver 20 only if the associated radio link is functioningcorrectly. If this is not the case, this is detected by the linkdetection means contained in transceiver 20, and in response thereto, asignal is transmitted from transceiver 20 to adjustment-messagegenerating means 23. The latter generate an adjustment message and sendit to transceiver 20 for transmission via radio link 5 or 6. Theadjustment message then arrives either at base station 1 or at basestation 3 in order subsequently to be processed therein and/ortransmitted to a higher-ranked entity.

The remarks inserted in the description of FIG. 2 relate to the buffersto be added to units and the optional additional processor forcontrolling the units also apply, to a greater or lesser extent, tomobile terminal 2.

The signalling message 30 shown in FIG. 4 comprises a section 31 whichcomprises, for example, a parameter for indicating the transmission ofthe message to higher- or lower-ranked entities, and it comprises asection 32 which comprises, for example, a further parameter forindicating whether the message is a signalling message or an adjustmentmessage. Furthermore, signalling message 30 comprises a section 33 whichcomprises the destination code (the first, second, third, fourthdestination code or the base-station destination code or the terminaldestination code or another destination code, etc.) and a section 34which comprises the actual signalling message.

The first and third destination code may either correspond to oneanother entirely or differ to a greater or a lesser extent. Only thefact that the processor device is able to recognize both destinationcodes as being destined for it is of importance. The first, second,third and fourth destination code may furthermore be of the explicit orof the implicit type.

In the case of destination codes of the explicit type, one particularbase station or particular processor device is indicated, thepossibility even arising that a mobile terminal transmits a signallingmessage provided with a second destination code to a base station A,said second destination code relating to a base station B, after whichthe base station A transmits said signalling message to a processordevice which then transmits the signalling message to the base stationB. In this procedure, the use of the parameter contained in section 31is advantageous because, in transmitting from the mobile terminal to thebase station A and from the base station A to the processor device, saidparameter indicates that the signalling message is on its way to ahigher-ranked entity. After receiving the signalling message, theprocessor device must arrange to alter said parameter in value toindicate that the signalling message is on its way to a lower-rankedentity (base station B). In this last case, it is therefore true that asecond destination code together with a parameter forms a seconddestination code in one sense, while said second destination codetogether with a parameter forms a base-station destination code inanother sense.

In the case of destination codes of the implicit type, for example, atype of entity (base station, processor device) or a type offunctionality (for example, call handling) is indicated, the basestation and processor device having to be preprogrammed with datarelating to which type of entity they are and with data relating to thefunctionalities which it is possible to carry out on the spot.

The adjustment message 40 shown in FIG. 5 comprises a section 41 whichcorresponds, for example, to section 31, and a section 42 whichcorresponds, for example, to section 32. As regards the parametercontained in section 41, the same is true as for the parameter containedin section 31, and the further parameters contained in sections 32 and42 will often have mutually inverse values. Furthermore, adjustmentmessage 40 comprises a section 43 which comprises, for example, thedestination code of the old base station (from before a handoverprocedure), a section 44 which comprises, for example, the destinationcode of the new base station (from after a handover procedure), and asection 45 which comprises, for example, the destination code of themobile terminal. Other data can be incorporated in section 46.

The options of using parameters contained in sections 31, 41 and 32, 42and further parameters will result in an extension of all the generatingmeans and adjustment-message generating means for the further generationof a further parameter for indicating whether the message is asignalling message or an adjustment message and for further generating aparameter for indicating transmission of the message to higher- orlower-ranked entities, and in an extension of, for example, comparisonmeans contained in the base station and detection means for furtherdetecting a parameter for indicating transmission of the message tohigher- or lower-ranked entities and for further detecting a furtherparameter for indicating whether the message is a signalling message oran adjustment message. These options reduce, in particular, the size ofand/or the number of analytical processes in base stations.

The adjustment messages which came up earlier in the discussion of FIG.2 and FIG. 3 will, in general, not be generated as a consequence of thesudden occurrence of a temporary link fault, but will often form acomponent of a complete handover procedure. In the section below, it isassumed that mobile terminal 2 generates the adjustment message.

A backward handover procedure proceeds as follows. Link detection meanswhich are associated with transceiver 20 and continuously monitor radiolink 5 and compare the quality thereof with other radio links to otherbase stations, detect, at a given instant, that the quality of radiolink 5 to base station 1 is appreciably poorer than the quality of radiolink 6 to base station 3. At the same time, the identification of basestation 3 is consequently known at mobile terminal 2. Mobile terminal 2then transmits a first adjustment message to base station 1 and a secondadjustment message via base station 1 to processor device 4. Of course,both adjustment messages may also coincide, in which case base station 1has to pass said adjustment message to processor device 4. At the sametime, radio link 6 is set up between base station 3 and mobile terminal2. In response to the adjustment message, a signal is transmitted, forexample, via comparison means 13 and/or processor 16 to return means 18which, starting from that instant, return all the signalling messagesdestined for mobile terminal 2 to processor device 4 which, via theadjustment message, is informed of the fact that all the signallingmessages should be transmitted to mobile terminal 2 via base station 3from now on.

A forward handover procedure, in which radio link 5 is consequentlysuddenly interrupted completely, proceeds as follows. Radio link 6between base station 3 and mobile terminal 2 is set up as quickly aspossible as a result of the continuous comparison made by the linkdetection means associated with transceiver 20. Mobile terminal 2 thentransmits an adjustment message to base station 3, which has to dispatchsaid adjustment message to processor device 4 or transmits an adjustmentmessage to processor device 4 via base station 3. Processor device 4 isinformed in this way of the fact that all the signalling messages haveto be transmitted to mobile terminal 2 via base station 3 from now on.Furthermore, processor device 4 should either be able to pass theadjustment message to base station 1 or it should be able to transmit asignalling message provided with a base-station destination code to basestation 1 in order to inform said base station 1 of the handoverprocedure performed. Because link detection means associated withtransceiver 10 have also detected the disappearance of radio link 5, allthe signalling messages provided with a terminal destination code arenot lost but are still stored in return means 18 or have already beenreturned to processor device 4.

Prior to the generation of an adjustment message, "negotiations" couldbe carried out between all the entities. This is done on the basis ofthe signalling messages which are provided with destination codes andare exchanged between the entities concerned.

As discussed in the case of the forward handover procedure, adjustmentmessages may also originate from, for example, a processor device orfrom a still higher-ranked entity. They may also originate from a basestation. However, in all these cases, various signalling messages oftenhave to be exchanged beforehand because, in the case of a certain old ornew base station, the identity of the new or old base station will notalways be known and because, in the case of a higher-ranked entity, both-identities will not always be known.

We claim:
 1. A mobile telecommunications system comprising:at least oneprocessor device for processing signaling messages; at least one basestation coupled to the processor device; and at least one mobileterminal which can be coupled to the base station, wherein signalingmessages include a destination code field, wherein a signaling messageto be transmitted from the mobile terminal to the processor device viathe base station is provided with a first destination code in itsdestination code field and a signaling message to be transmitted fromthe mobile terminal to the base station is provided with a seconddestination code in its destination code field, wherein the base stationis provided with comparison means for comparing a value in thedestination code field of a signaling message with at least onepredetermined value and, in response to a comparison result in onesense, transmitting the signaling message in the direction of theprocessor device and, in response to a comparison result in anothersense, retaining the signaling message for internal processing, whereina signaling message to be transmitted from the base station to theprocessor device is provided with a third destination code in itsdestination code field, wherein the processor device includes comparisonmeans for comparing the value in the destination code field of thesignaling message with at least one predetermined value and fortransmitting the signaling message, in response to a comparison resultin one sense, and, in response to a comparison result in another sense,for retaining the signaling message, wherein signaling messages to betransmitted from the processor device to the mobile terminal via thebase station are provided with a terminal destination code field,wherein signaling messages to be transmitted from the processor deviceto the base station are provided with a base station destination codefield, and wherein the base station is provided with detection means fordetecting base station destination codes and, in response thereto,retaining a signaling message and for detecting terminal destinationcodes and, in response thereto, transmitting a signaling message in thedirection of the mobile terminal.
 2. The mobile telecommunication systemaccording to claim 1, wherein the processor device includes:memory meansfor storing at least one coupling between a terminal destination codeand a base station destination code for each mobile terminal; andadjustment means coupled to the memory means for adjusting, in responseto an adjustment message, at least one coupling stored in the memorymeans, and wherein the base station further includes:link detectionmeans for detecting whether or not a link between the base station andthe mobile terminal is functioning well; and return means coupled to thelink detection means for returning a signaling message provided with aterminal destination code to the processor device in response to ithaving been detected that the link is not functioning well.
 3. Themobile telecommunication system according to claim 2, wherein the basestation further includes adjustment-message generating means coupled tothe link detection means for generating an adjustment message.
 4. Themobile telecommunication system according to claim 2, wherein the mobileterminal includes:link detection means for detection whether or not alink between the base station and the mobile terminal is functioningwell; and adjustment-message generating means coupled to the linkdetection means for generating an adjustment message.
 5. A base stationfor use in a mobile telecommunication system, the base stationcomprising:a) comparison means for comparing first and seconddestination codes of signaling messages originating from a mobileterminal with at least one predetermined value; b) means fortransmitting, in response to a comparison result in one sense, asignaling message in the direction of a processor device and, inresponse to a comparison result in another sense, for retaining asignaling message for internal processing; c) generating means forgenerating a signaling message having a third destination code and beingdestined for the processor device; and d) detection means for detectingbase station destination codes and, in response thereto, retaining asignaling message, and for detecting terminal destination codes and, inresponse thereto, transmitting a signaling message in the direction of amobile terminal.
 6. The base station according to claim 5 furthercomprising:e) link detection means for detecting whether or not a linkbetween the base station and the mobile terminal is functioning well;and f) return means coupled to the link detection means for returning asignaling message provided with a terminal destination code to theprocessor device in response to it having been detected that the link isnot functioning well.
 7. The base station according to claim 6 furthercomprising:g) adjustment-message generating means coupled to the linkdetection means for generating an adjustment message.